Our understanding of cortical function is largely static and modular. A lot has been learned about which cortical areas express different types of information, but how information flows through the cortex is still largely conjecture, indirectly inferred from anatomical connections. Consider two critical cognitive functions: attention and perceptual decisions. Much is known about these functions on a modular level, but where these signals arise, where they flow, and how brain areas interact and collaborate to support them is still largely unknown. To address this, we will train monkeys to make judgments about visual motion and/or color in a task designed to parametrically vary attention and decision factors. We will record neural activity from many electrodes simultaneously implanted in a wide range of areas in the frontal and visual cortex. By comparing temporal dynamics of neural activity, we will test fundamental hypotheses about the nature of how cognitive signals arise and act on different cortical areas. One hypothesis is that both attention and decision-related signals arise from prefrontal cortex and flow to visual cortex. The alternative hypothesis is that top-down attention signals arise in the prefrontal cortex, but perception decisions arise in higher-level visual cortex. We will also determine whether top-down signals act simultaneously on different levels of the cortical hierarchy versus the signals cascading from one area to the next. We will also test whether patterns of signal flow and interactions between cortical areas change with task demands. Testing these hypotheses is critical step to addresses neuropsychiatric disorders. There is increasing evidence that many disorders may be due to dysfunction in connections and interactions between brain areas. This study would be the first large scale test of how interactions between cortical areas support two basic and critical cognitive functions in the normal brain.